Manufacture of articles from malleable cast iron



Patented Aug. 24, 1937 UNITED STATES PATENT OFFICE MANUFACTURE or Aarrcms mom- MAL- mAsm c s'r mos Karl Roesch and sch Otto Josef schleim er, nemeid, Germany No Drawing. Application May 1'1, 1985, Serial 4 No. 22,114. In Germany October 31,1984

2 Claims. (c1. nil-21.8)

ferritic or pearlitic structure practically free from temper carbon to castings containing from 2.2 to 3.2% carbon, less than 0.6% silicon, from 0.15 to 1.2% manganese, and less than 0.1% sulphur by subjecting them to an oxidizing annealing.

treatment in which decomposition of the iron carbide is. suppressed and the carbon is directly removed fromthe cementite. The low silicon content prevents the formation of temper carbon which previously made welding of malleable cast iron practically impossible, and it' also improves the quality of the weld. The low sulphur content suppresses the formation of sulphur dioxide gas and the med-shortness normally brought about during welding by a high sulphur content, and thus prevents the occurrence of holes and pores in the weld.

It has now been found that it is preferable to adjust the manganese content in accordance with an absolutely definite law. According to the invention the manganese content in thepig iron is at least equal to twice the silicon content, and preferably equal to the sum of twice "the silicon content and three times the sulphur content. A pig iron with 0.6% silicon and 0.10% sulphur should accordingly contain at least 1.2% and preferably 1.5% manganese. I

If this law is observed it has been found that it is no longer necessary to adhere so closely to the low silicon and sulphur contents as is stated in our application Ser. No. 739,056, a fact which much facilitates the melting of the cast iron. It .has now been found that the capacity of the malleable caste-iron for being satisfactorily welded does not suffer if the silicon content of the casting is as high as 0.8% and the sulphur content as high as 0.15%. The corresponding manganese content according to this invention is then at least 1.6% and preferably 2%. A manganese content higher than 2% is not desirable.

If the manganese content of the pig iron is adjusted as described up to a total content of 2% the eifect on the capacity of the malleable cast iron for being welded is very satisfactory. This is due to the fact that in comparison with normal malleable cast iron the pig iron is completely deoxidized straight away by the high manganese content. In particular, over-oxidation of the surface layers is avoided by the powerful decarboniz'ation that is effected during the temper process by the manganese in combination with the unusually low silicon content, and

this is very important for good and reliable welding. Moreoventhe high manganese content leads to a fluid slag during welding. which is desirable. Finally the manganese helps to prevent the decomposition' of the carbide and coniblues with the sulphur to form manganese sulphide which is harmless. Therefore a high manganese content makes it possible to use a somewhat higher. silicon content without there being any need to fear precipitation of carbide, and

also allows the use of a somewhat higher sulphur content.

Finally, the fused metal produced on welding malleable cast iron made according to the invention runs easily and adheres well to the work, so that even overhead welding can be carried on without much difnculty.

The invention is particularly applicable to the manufacture of thin-walled articles, i. e. articles of wall thickness less than an inch and in which decarbonizatlon throughout the whole cross-section can be eflected by the temper process.

We claim; 1. The process of producing articles that can be satisfactorily welded, which comprises packing iron castings containing 2.2-3.2% carbon,

vcontaining silicon in an amount not exceeding 0.8%, containing sulphur in an amount not exceeding 0.15%, an amount of manganese that is at least equal. to twice the silicon, content but not more than 2%, and the remainder iron and the usual content of phosphorus, in iron oxide material and subjecting them to an oxidizing annealing treatment, whereby decomposition of the -iron carbide is suppressed and the carbon is directly removed from the cementite.

2; The process of producing articles that can be satisfactorily welded, which comprises packing iron castings containing 22-33% carbon, containing silicon in an amount not exceeding 0.8%, containing sulphur in an amount not exceeding 0.15%, an amount of manganese that is. equal to at least the sum of twice the silicon content and three times the sulphur content but not substantially more than 2%, and the remainder iron and the usual content of phosphorus, in iron oxide material and subjecting them to an oxidizing annealing treatment, whereby decomposition of the iron carbide is suppressed and the carbon is directly removed from the cementite.

KARL ROESCH. o'rro JOBEF scmmmn. 

